1. Field of the Invention
The present invention relates to an apparatus for compensating for the detection accuracy of a fuel pressure sensor which is capable of detecting the pressure of a supplied fuel in a spark-ignition direct-injection type internal combustion engine, etc., in which the fuel supplied by a fuel pump is directly injected into a combustion chamber in each engine cylinder.
2. Description of the Related Art
Such a kind of conventional apparatus is shown in Japanese Patent Application Laid-Open No. 11-50903 for instance. In an accumulator fuel injection apparatus disclosed therein, an internal combustion engine equipped with the accumulator fuel injection apparatus is run in a steady-state operation so as to compensate for deterioration in the detection accuracy owing to manufacturing tolerances, aging, etc., of a fuel pressure sensor. An output deviation in the fuel pressure sensor is compensated for by calculating a compensation value for the fuel pressure sensor based on an instructed fuel pressure value and an estimated fuel pressure value, or based on an instructed fuel injection amount and an actual fuel injection amount, or based on a change rate of an instructed fuel pressure value and a change rate of an instructed fuel injection amount, or based on an estimated engine rotational speed and an actual engine rotational speed.
In such a conventional apparatus, however, the above measure has been taken for compensation of the gain characteristic of the fuel pressure sensor, but no consideration is given to compensating for an output deviation of the fuel pressure sensor resulting from an offset thereof. That is, when there takes place deterioration in the detection accuracy of the fuel pressure sensor resulting from the sensor offset, even if the sensor gain has been compensated for in a certain steady-state operation of the internal combustion engine, the detection accuracy of the sensor might contrarily be deteriorated when the engine gets out of the steady-state condition in which the sensor gain was compensated.